This invention relates to a method of controlling an automatic sewing machine in which a cloth retainer holding a workpiece such as a piece of cloth is moved along a predetermined configuration with the aid of memory elements, thereby to provide a seam along the predetermined configuration, and a device for practicing the method.
FIG. 1 shows an external appearance of a conventional ordinary automatic sewing machine. The automatic sewing machine comprises: a sewing mechanism section 25 on a sewing table 201 which incorporates a mechanism for forming a seam on a material to be sewed (herein after referred to as "a sewing material", when applicable) with a needle bar 202; an electric motor 203 for driving the sewing mechanism section; a cloth retaining unit 206 for holding a sewing material between an upper retaining board 204 and a lower retaining board 205 with the aid of air; and a biaxial drive mechanism 208 for two-dimensionally moving the cloth retaining unit 206 on a slide board 207 according to a predetermined pattern. A control unit 209 for controlling the operations of the above-described components is provided in the form of two parts, upper and lower parts, on one side of the sewing table 201. The upper part of the control unit 209 comprises: an operating panel 210 on which a variety of switches for controlling the operations of the automatic sewing machine are provided; and a data reading device for reading data from a memory medium 6 inserted thereinto in which data on the patterns of movement of the biaxial drive mechanism have been stored. That is, the upper part of the control unit operates to control the operation timing of the entire sewing machine, and the movement of the biaxial drive mechanism 208.
More specifically, the operating panel 210 has power switches 211, a reset switch 212 positioning the biaxial drive mechanism 208 in place and resetting the system, and a test switch 213 for performing a biaxial drive with the needle bar maintained stopped.
A start switch 217 for providing a sewing start instruction, and a switch 214 for holding the cloth retaining unit 206 (hereinafter referred to as "a cloth retaining switch 214", when applicable) are provided below the sewing machine body. The aforementioned sewing mechanism section 25 has a stop switch 215 for stopping a sewing operation. The biaxial drive mechanism 208 has original point detecting units 29 and 30 for detecting the mechanical original point of two axes.
FIG. 2 is a block diagram showing the arrangement of the conventional control unit 209.
In FIG. 2, reference numeral 1 designates a central arithmetic unit (hereinafter referred to as "a CPU 1", when applicable); 32, a crystal oscillator for forming a clock signal for the CPU 1; 2, an integrated circuit for latching an address provided by the CPU 1 (hereinafter referred to as "an address latching circuit 2", when applicable, which is 74LS373 for instance); 3, an integrated circuit for buffer for transmitting data between the CPU 1 and memory (hereinafter referred to as "a memory data buffer 3", when applicable, which is 74LS245 for instance); 4, an integrated circuit for buffer for transmitting data between an input/output interface element 8 (hereinafter referred to as "an I/O 8", when applicable) and the CPU 1 (hereinafter referred to as "a peripheral data buffer 4", when applicable, which is 74LS245 for instance); 5, an IC select signal generating circuit for producing IC select signals for selecting memories and peripheral elements; 6, a RAM used for a stack in the execution of a program for instance; 7-a, a ROM storing programs; 7-b, a nonvolatile memory unit in which sewing patterns are stored (hereinafter referred to as "a pattern ROM 7-b", when applicable); 8, the aforementioned I/O serving as an interface in response to instructions from the CPU; 15, a group of switches; and 9, a circuit which receives data through the I/O 8 to control the motor 203 for rotating the spindle of the sewing machine.
Further in FIG. 2, reference numeral 10 designates an input interface circuit for shaping the output signal waveform of the detector 26 which detects the speed of rotation of the spindle of the sewing machine and the position of the needle bar 202; 12, an input interface circuit for shaping the output signal waveform of a foot switch assembly 31; 13, a drive circuit for driving pulse motors 27 and 28 to operate the biaxial drive mechanism 208; 14, a drive circuit for driving a solenoid or electromagnetic valve 23 to operate the cloth retaining unit and a thread cutting unit; and 16, an electric power circuit for supplying electric power to all of the circuits in the sewing machine.
The operation of the automatic sewing machine thus constructed will be described.
First, the power switch 211 of the control unit 209 is turned on to start the motor 203. At the same time, electric power is supplied to the electric power circuit 16 in the circuit (FIG. 14) of the control unit 209, to start the control circuit. First, the CPU 1 reads from the ROM 7-a a program for initially setting itself and the I/O 8, and initially sets them. Thereafter, the reset switch 212 in the group of switches is closed, so that the CPU 1 receives the information through the I/O 8, and operates the pulse motors 27 and 28 through the I/O 8 to operate the biaxial drive unit 208. Thereafter, the biaxial drive unit 208 is driven until the original point detecting units 29 and 30 provide original point signals, so that the biaxial drive unit is moved to a predetermined position (hereinafter referred to as "a mechanical original point", when applicable). Under this condition, the operator or sewing person sets the sewing material between the upper and lower retaining boards 204 and 205, so that the sewing material is positioned in place. When the cloth retaining switch 214 in the foot switch assembly 31 is closed, the CPU 1 receives the signal through I/O 8, and operates the electromagnetic valve 23 through the I/O 8 to activate a pressure plate 216, so that the upper retaining board 204 is moved downwardly; that is, the sewing material is held between the upper and lower retaining boards 204 and 205. Thereafter, when the start switch 217 in the foot switch assembly 31 is closed, a signal is applied through the I/O 8 to the CPU 1, so that the CPU 1 reads one of ten pattern data which are programmed in the ROM 7-b in advance and limited by the group of switches 15. According to the data thus read, the CPU 1 drives the biaxial drive unit 208 through the I/O 8, and operates the motor 203 through the I/O 8 to drive the sewing mechanical section 25, as a result of which a seam is formed on the sewing material in accordance with the predetermined pattern.
After the sewing operation, the CPU 1 applies a drive signal through the I/O 8 to the thread cutting solenoid 23, to cut the thread. Thereafter, the motor 24 is stopped, and the sewing mechanical section 25 is stopped. The cloth retaining unit electromagnetic valve 23 is turned off, and the cloth retaining unit 206 releases the sewing material.
The conventional automatic sewing machine control device is designed as described above. Therefore, the capacity of the ROM 7-b is insufficient, being 128 k bytes in maximum. In addition, it is rather troublesome to handle the ROM, because it may be broken when held directly with the hand. In order to eliminate the difficulties, Japanese Patent Application (OPI) No's 6097/1984, 226356/1987 and 51366/1983 (the term "OPI" as used herein means an "unexamined published application") have proposed a method in which magnetic memory means are used to store sewing pattern data (hereinafter referred to as "FDs", when applicable). However, employment of the FDs is not welcome by the users using an automatic sewing machine control device with a ROM in which sewing pattern data are stored, because the FD is not interchangeable with the ROM.
Furthermore, the employment of the FDs suffers from the following difficulties. The control device using the FD is liable to be adversely affected by variation of environmental conditions, or it is liable to erroneously operate when the power supply is interrupted momentarily. With a system using a floppy disk, the floppy disk must be rotated when the power source is turned on, as a result of which the system is relatively short in service life.
Furthermore, in the conventional automatic sewing machine control device, the group of switches 15 are used to select sewing patterns and to set sewing speeds, and the foot switch assembly 31 is operated to retain a sewing material and to start the sewing machine. Therefore, it is necessary to provide one operator for one or two automatic sewing machines, and it is rather difficult to realize the unmanned operation of the automatic sewing machines.